When a child boarded Charles Albert Poland Jr.’s bus, “they were no longer their parents’, they were his,” Aaron Poland told NBC News. “And I know that’s the reason why my dad took those shots. It was for his children, just like he would do for me and my sister.”

Authorities say Jimmy Lee Dykes, a Vietnam veteran and survivalist, boarded Poland's bus on Tuesday and demanded two children. When Poland refused, Dykes shot him, authorities say. They say Dykes took a 5-year-old boy hostage and has been holed up in an underground bunker with him ever since.

Poland, 66, had driven a school bus for Dale County since 2009. Authorities said they found four shell casings at the scene.

"I expected them to say he had a heart attack or got in to a car wreck. Never in my wildest dreams did I think he'd get shot, and shot four times," Poland's sister, Vicki Upchurch, said Thursday.

Upchurch, who lives in Athol, Idaho, told NBC station KHQ of Spokane, Wash., that Poland family grew up in northern Idaho, where much of the family still lives. Relatives were planning to travel from Idaho to Alabama for his funeral services this weekend.

"We will get through this," Upchurch said. "My brother was very religious. He had a deep faith."

Poland joined the Army in the 1960s and moved to Alabama, where he married and had lived ever since, Upchurch said. She said he retired as a diesel mechanic in 2009 and had been driving a school bus to help support his wife until she was able to retire.

"My brother would have done anything to protect those kids," she said.

Schools Superintendent Donny Bynum said in a statement Wednesday that "Mr. Poland was well-loved by all of us here at Dale County Schools."

While neighbors have described Dykes, 65, as a paranoid survivalist who was always digging in his yard with a shovel, Poland's neighbor Hilburn Benton told the Eagle that the bus driver once helped him complete a major yard project and asked nothing in return.